U.S. patent application number 14/417561 was filed with the patent office on 2015-07-30 for dryer fabric.
The applicant listed for this patent is VOITH PATENT GMBH. Invention is credited to Juergen Abraham, Anas Alias.
Application Number | 20150211179 14/417561 |
Document ID | / |
Family ID | 48875048 |
Filed Date | 2015-07-30 |
United States Patent
Application |
20150211179 |
Kind Code |
A1 |
Alias; Anas ; et
al. |
July 30, 2015 |
DRYER FABRIC
Abstract
A papermaking dryer fabric has a system of MD yarns interwoven
with a system of CMD yarns in a single layer weave. The MD yarns
have groups each formed of a plurality of adjacent MD yarns weaving
in the group side-by-side the same weave path with the CMD yarns.
The dryer fabric is flat woven with seaming loops at the widthwise
edges of the fabric to make it endless. At least some of the
seaming loops are formed by at least some MD yarns of the groups of
MD yarns. The MD yarns forming the groups of MD yarns have a
circular cross section and the CMD yarns are ungrouped CMD yarns
and at least some of said CMD yarns have a non-circular cross
section with a width to height ratio of more than 1. The dryer
fabric has an air permeability between 25 cfm and 200 cfm.
Inventors: |
Alias; Anas; (Ipoh, MY)
; Abraham; Juergen; (Nattheim, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VOITH PATENT GMBH |
HEIDENHEIM |
|
DE |
|
|
Family ID: |
48875048 |
Appl. No.: |
14/417561 |
Filed: |
July 25, 2013 |
PCT Filed: |
July 25, 2013 |
PCT NO: |
PCT/EP2013/065672 |
371 Date: |
January 27, 2015 |
Current U.S.
Class: |
162/289 |
Current CPC
Class: |
D21F 1/0027 20130101;
D21F 7/12 20130101; D21F 1/0054 20130101 |
International
Class: |
D21F 7/12 20060101
D21F007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 2012 |
FI |
20125819 |
Claims
1-14. (canceled)
15. A papermaking dryer fabric, comprising: a system of MD yarns
interwoven with a system of CMD yarns in a single layer weave; said
MD yarns including groups of MD yarns, with each of said groups of
MD yarns being formed by a plurality of adjacent MD yarns weaving
in said group side-by-side a same weave path with said CMD yarns,
said MD yarns forming said groups of MD yarns having a circular
cross section; said CMD yarns being ungrouped CMD yarns and at
least some of said CMD yarns having a non-circular cross section
with a width to height ratio of more than 1; wherein the dryer
fabric is flat woven with seaming loops arranged at widthwise edges
of the fabric and formed in an endless dryer fabric, and wherein at
least some of said seaming loops are formed by at least some MD
yarns of said groups of MD yarns, and wherein the dryer fabric is
formed to have an air permeability of between 25 cfm and 200
cfm.
16. The papermaking dryer fabric according to claim 15, wherein
said single layer weave is a plain weave.
17. The papermaking dryer fabric according to claim 15, wherein all
of said CMD yarns have a non-circular cross section with a width to
height ratio of more than 1.
18. The papermaking dryer fabric according to claim 15, wherein all
of said MD yarns form said groups of MD yarns.
19. The papermaking dryer fabric according to claim 15, wherein
each said group of MD yarns is formed by four or fewer adjacent MD
yarns weaving side-by-side the same weave path with said CMD
yarns.
20. The papermaking dryer fabric according to claim 19, wherein
each said group of MD yarns is formed by two or three MD yarns.
21. The papermaking dryer fabric according to claim 15, wherein
said CMD yarns have a shape selected from the group consisting of a
bone-shape, a rectangular cross section shape, and a double convex
shape.
22. The papermaking dryer fabric according to claim 15, wherein
said width to height ratio is 1.5 or more.
23. The papermaking dryer fabric according to claim 15, wherein
said CMD yarns have a height of 0.5 mm or more.
24. The papermaking dryer fabric according to claim 23, wherein
said CMD yarns have a height of between 0.5 mm and 1.1 mm.
25. The papermaking dryer fabric according to claim 23, wherein
said CMD yarns have a height of between 0.6 mm and 1.0 mm.
26. The papermaking dryer fabric according to claim 23, wherein
said CMD yarns have a height of between 0.7 mm and 0.9 mm.
27. The papermaking dryer fabric according to claim 15, wherein
said MD yarns have a diameter between 0.5 mm and 0.8 mm.
28. The papermaking dryer fabric according to claim 27, wherein
said MD yarns have a diameter between 0.55 mm and 0.65 mm.
29. The papermaking dryer fabric according to claim 15, wherein
said air permeability of the fabric lies between 50 cfm and 200
cfm.
30. The papermaking dryer fabric according to claim 29, wherein
said air permeability of the fabric lies between 50 cfm and 150
cfm.
31. The papermaking dryer fabric according to claim 15, wherein at
least some of said CMD yarns comprise a two-phase polymeric
material, with a first polymeric phase melting at a first
temperature and a second polymeric phase melting at a second
temperature higher than the first temperature, and wherein the
fabric has the characteristics of having been subjected to a heat
setting treatment at a temperature at or above the first
temperature and below the second temperature.
32. The papermaking dryer fabric according to claim 15, wherein the
fabric has two widthwise edges each provided with seaming loops
formed by two MD yarns, wherein the fabric further has binder loops
each being formed by two MD yarns, and wherein a binder loop is
located between two adjacent seaming loops and vice versa.
33. The papermaking dryer fabric according to claim 32, wherein
each of said seaming loops is formed by first and second MD yarns,
and said first and second MD yarns are from the same group of MD
yarns.
34. The papermaking dryer fabric according to claim 32, wherein
each of said seaming loops is formed by a first MD yarn from a
first group of MD yarns and by a second MD yarn from a second group
of MD yarns adjacent to the first group of MD yarns.
Description
[0001] The present invention relates to a papermaking dryer fabric
for use in a dryer section of a papermaking machine.
[0002] Modern dryer fabrics especially for use in high speed
papermaking machines with production speeds of 1200 meters per
minute or more need to have relatively low air permeability, low
inner void volume and low caliper for low air carriage. The weaving
structure of such dryer fabrics has to have as less as possible
intersections for low affinity of contamination. Further on such
dryer fabrics must guaranty sufficient bending stiffness in the
cross-machine direction (CMD) of the fabric.
[0003] In the state of the art several attempts for dryer fabrics
are known. EP1736595 discloses e.g. a dryer fabric with weft yarns
grouped in pairs and with ungrouped warp yarns as well as with weft
and warp yarns grouped in pairs. Such fabrics have improved
performance due to less water and air carriage, but have the
disadvantage that the weaving process of such fabrics is difficult
to control because of the parallel insertion of weft yarns which
sometimes tend to overly each other instead of weaving parallel to
each other.
[0004] U.S. Pat. No. 5,799,708 discloses a papermaking fabric with
flat shaped warp yarns which are grouped in pairs and with round
shaped weft yarns which are ungrouped. Such fabrics have the
disadvantage that the forming of seaming loops is difficult,
because of the rectangular shape of the warp yarns which tend to
twist during the formation of the seam loops. During the joining
process of such fabrics in the papermaking machine the twisted
seaming loops are difficult to interdigitate and to put a pintle
through them.
[0005] What is needed is a new dryer fabric design with low water
and air carriage, which is easy and controllable to manufacture and
easy to join during installation in the papermaking machine.
[0006] The problem is solved with a papermaking dryer fabric
comprising a system of MD yarns interwoven with a system of CMD
yarns in a single layer weave, said fabric comprising groups of MD
yarns, wherein each group being formed by a plurality of adjacent
MD yarns having a circular cross section and weaving in said group,
like a single yarn, side-by-side the same weave path with said CMD
yarns. The dryer fabric according to the invention further has only
ungrouped CMD yarns which have a non-circular cross section with a
width to height ratio of more than 1. The dryer fabric according to
the invention further has a air permeability between 25 and 200
cfm.
[0007] The CMD yarns are ungrouped or in other words, adjacent CMD
yarns weave different weave paths with the MD yarns. Therefore the
weaving process is controllable in a reliable manner. Due to use of
flat CMD yarns or in other words, CMD yarns with a width to height
ratio of more than one, a low calliper fabric can be achieved
combined with a reduced number of CMD/MD yarn intersections to
provide a fabric with a reduced contamination affinity. Further on
the flat CMD yarns give the ability to control or reduce the air
permeability of the fabric in a certain range based on the specific
choice of the width of the CMD yarns. For a controllable weaving
process the maximum width of the CMD yarns is limited 3-4 mm. To
further control or reduce the air permeability of the fabric, the
invention proposes grouped MD yarns which have a circular cross
section, to guaranty untwisted seaming loops and to make joining
more easy.
[0008] Preferred embodiments of the present invention are further
described in the sub-claims.
[0009] According to a preferred embodiment of the invention the
single layer weave is a plain weave. A plain weave provides a
homogenous weaving structure with low making issues to the paper
web that comes into contact with the paper-side of the dryer
fabric. A plain weave pattern further gives a highly stable fabric
with a high rigidity.
[0010] To further influence the air permeability of the dryer
fabric preferably all CMD yarns of the fabric have a non-circular
cross section with a width to height ratio of more than 1.
[0011] Preferably all MD yarns form said groups of MD yarns. This
further increases the ability to reduce the air permeability to the
lower edge of the claimed range and can e.g. lead to air
permeability values of 150 cfm or lower.
[0012] To achieve that the grouped MD yarns lie in parallel next to
each other without overlapping each other, preferably each of the
groups of MD yarns is formed by four or less adjacent MD yarns,
preferably by two or three MD yarns weaving side-by-side the same
weave path with said CMD yarns.
[0013] The non-circular CMD yarns for example can have a bone-like
cross section (remark: in some prior art documents also called
bi-nodal cross section). It is further possible that the
non-circular CMD yarns have a rectangular cross section. Further on
it is possible that the non-circular CMD yarns have a double convex
shaped cross section, wherein double convex shaped means that the
cross section consists of two convex halves which cross each other
at an angle of more than 0.degree. and less than 180.degree.. The
width to height ratio can be 1.5 or more. Preferably the width to
height ratio is not more than 2.0 to 4.0.
[0014] One of the advantages of ungrouped CMD yarns with
non-circular cross section compared to grouped CMD yarns with
circular cross section is, that the air permeability can be further
reduced without increasing the thickness of the yarns and therefore
the thickness of the fabric. Another advantage is that one flat CMD
yarn has a smooth surface whereas grouped CMD yarns always generate
some gap between them which can serve as traps for
contamination.
[0015] Especially for high speed applications it is advantageous if
the dryer fabric has a high CMD stiffness. To achieve a high CMD
stiffness the inventors found out, that the height of the CMD yarns
with non-circular cross section preferably should not be below 0.5
mm. To make a sufficiently thin dryer fabric with reduced water and
air carriage it is further advantageous is the fabric has a
thickness of not more than 1.1 mm. According to a preferred
embodiment of the invention it is foreseen, that the thickness of
the CMD yarns preferably is between 0.5 mm and 1.1 mm, more
preferably between 0.6 mm and 10.mm, most preferably between 0.7 mm
and 0.9 mm.
[0016] To achieve a good balance between low fabric calliper and
easy bending of the MD yarns to form the seam loops on the one hand
and sufficient stability of the MD yarns to withstand the drive
load the fabric is subjected to, the inventors found out that for
the dryer fabric design of the present invention it is
advantageous, if the MD yarns have a diameter between 0.5 mm and
0.8 mm, preferably between 0.55 mm and 0.65 mm.
[0017] To further reduce water and air carriage it is advantageous
if the air permeability of the fabric is between 50 cfm and 200
cfm, preferably between 50 cfm and 150 cfm.
[0018] Table 1 shows a comparison of the properties between a dryer
fabric known from EP1736595 (conventional fabric) and a preferred
embodiment of a dryer fabric according to the present invention,
were all design features except the one expressively indicated as
being different are identical.
TABLE-US-00001 TABLE 1 Weave design: plain weave Paired MD yarns:
PET/diameter 0.6 mm/160 to 190 MD yarns per 100 mm CMD yarns: i)
conventional fabric PET/diameter 0.8 mm/paired ii) invention fabric
PET/height 0.6 mm/width 1.4 mm/ungrouped Rem: conventional fabric
number of CMD yarn pairs Air permeability [cfm] invention fabric
number of (conventional dryer Air permeability CMD yarns fabric)
[cfm] (invention) 73 CMD yarns per 100 mm 150 75 70 CMD yarns per
100 mm 180 100 65 CMD yarns per 100 mm 240 140
[0019] The above disclosed embodiment of the fabric design
according to the invention gives the possibility to reduce the air
permeability by at least 40%.
[0020] The papermaking dryer fabric according to the present
invention can have at least some CMD yarns which comprise a
two-phase polymeric material, with a first polymeric material that
melts at a first temperature and a second polymeric material which
is substantially immiscible with the first polymeric material and
which melts at a second temperature which is lower than the first
temperature, wherein the fabric has been subjected to a heat
setting treatment at a temperature at or above the second
temperature and below the first temperature. Dryer fabrics
according to this embodiment can have a smoother paper contacting
surface due to the fact that during heat setting crimp, which is in
the MD or warp yarns after the weaving process can be more easily
transferred to the CMD or weft yarns. This is especially the case,
when the MD yarns are made from a material with a melting
temperature above the heat setting temperature.
[0021] The second material can include alone or in combination:
polyolefins, polyamides or fluoropolymers. The first material can
include alone or in combination: homopolymers or copolymers of
polyesters e.g. PET, polyamides or PPS.
[0022] According to a second aspect of the present invention a
method for producing packaging, board or cardboard is provided with
the following feature: [0023] Providing a fibrous slurry to at
least one forming fabric in a forming section and dewater the
slurry through the at least one fabric to form a fibrous web [0024]
transferring the fibrous web to a at least one pressfelt in a
pressing section and dewater the web through at least one press
felt [0025] transferring the web to a dryer fabric according to one
of the claims 1-14 in a dryer section and drying the web when the
web is sandwiched between the dryer fabric and a heated dryer
cylinder of the dryer section.
[0026] Due to the fact that the dryer fabric according to one of
the claims 1-14 has a low internal void volume combined with a
smooth surface with reduced number of yarn intersections the dryer
fabric is very easy to clean and has an excellent stay clean
performance and therefore preferably is usable in the production of
packaging, board or cardboard due to the fact that the fibrous
slurry for the production of packaging, board or cardboard web
often has a high recycled content.
[0027] Preferably the dryer fabric according to one of the claims
1-14 is used in at least one of the first, second or third dryer
group of the dryer section.
[0028] The invention will be further illustrated with the following
figures, wherein
[0029] FIG. 1 shows a top view onto a part of the dryer fabric
according to the invention,
[0030] FIG. 2 shows a cross sectional view in CMD direction of the
fabric of FIG. 1,
[0031] FIG. 3 shows a cross sectional view in MD direction of the
fabric of FIG. 1 with CMD yarns having a rectangular cross
section,
[0032] FIG. 4 shows a cross sectional view in MD direction of an
alternative fabric with CMD yarns having a bone-like cross
section,
[0033] FIG. 5 shows a cross sectional view in MD direction of an
alternative fabric with CMD yarns having a double convex shaped
cross section,
[0034] FIG. 6 shows top view onto a part of the dryer fabric as
seen in FIG. 1 with a first variant of seam loop construction
and
[0035] FIG. 7 shows top view onto a part of the dryer fabric as
seen in FIG. 1 with a second variant of seam loop construction.
[0036] FIG. 1 shows a top view onto a part of the dryer fabric 1
according to the invention. The fabric 1 has a system of MD yarns 2
interwoven with a system of CMD yarns 3 in a single layer weave. In
the embodiment shown in the FIGS. 1-3 the system of MD yarns only
consists of groups 4 of two adjacent MD yarns 3 which weave in each
group 4 side-by-side the same weave path with the CMD yarns 3. The
dryer fabric 1 is flat woven in a plain weave design.
[0037] As can be seen from FIGS. 1 and 2 the MD yarns 2 have a
circular cross section. As can be seen from FIGS. 1 and 3 all the
CMD yarns 3 are ungrouped--that means adjacent CMD yarns weave
different weave paths with the MD yarns 2--and have a rectangular
cross section with a width to height ratio of 2. The CMD yarns 3 in
the embodiment as shown in FIGS. 1-3 have a height of 0.6 mm,
wherein the MD yarns 2 have a diameter of 0.6 mm. The dryer fabric
shown can have a air permeability between 75 cfm and 140 cfm.
[0038] FIG. 4 shows a cross sectional view in MD direction of an
alternative fabric with CMD yarns 3a having a bone-like cross
section. The rest of the fabric of FIG. 4 is identical to fabric
shown in FIGS. 1 and 2.
[0039] FIG. 5 shows a cross sectional view in MD direction of an
alternative fabric with CMD yarns 3b having a double convex shaped
cross section. The rest of the fabric of FIG. 5 is identical to
fabric shown in FIGS. 1 and 2.
[0040] FIG. 6 shows top view onto a part of the dryer fabric as
seen in FIG. 1 with a first variant of seam loop construction. As
can be seen part of the MD yarns 2 form seaming loops 5 which are
arranged at the widthwise edges of the fabric 1 to make it endless.
The other part of the MD yarns 2 form so called binder loops 6 to
hold the widthwise fabric edges. As can be seen between adjacent
seaming loops 5 a binder loop 6 is located and vice versa. In the
embodiment as seen in FIG. 6 every seaming loop 5 and every binder
loop 6 is formed by MD yarns 2 of different groups 4. By way of
example one of the seaming loops 5 is formed by a MD yarn 2 of
group 4' and by a MD yarn 2 of group 4'' and adjacent binder loop 6
is formed by a MD yarn 2 of group 4'' and by a MD yarn 2 of group
4'''.
[0041] FIG. 7 shows top view onto a part of the dryer fabric as
seen in FIG. 1 with a second variant of seam loop construction. As
can be seen part of the MD yarns 2 form seaming loops 5 which are
arranged at the widthwise edges of the fabric 1 to make it endless.
The other part of the MD yarns 2 form so called binder loops 6 to
hold the widthwise fabric edges. As can be seen between adjacent
seaming loops 5 a binder loop 6 is located and vice versa. In the
embodiment as seen in FIG. 7 every seaming loop 5 and every binder
loop 6 is formed by MD yarns 2 of the same group 4. By way of
example one of the seaming loops 5 is formed by the two MD yarns 2
of group 4' and adjacent binder loop 6 is formed by the two MD
yarns 2 of another group 4''. To hold the widthwise fabric edges
this seam construction further has an additional end yarn 7 which
passes through the binder loops 6 and over or under the seaming
loops 5 without passing through them.
* * * * *